1. Field of the Invention
The present invention relates to an adjustable luminaire, and more particularly to a luminaire with adjustable height and illuminated area simultaneously.
2. Description of Related Art
A conventional adjustable luminaire in accordance with the prior art comprises a base, an arm pivoted to the base and carrying a lamp housing at its free end. The adjustable luminaire has a link supporting the arm and being also pivoted to the base and to a member which has a sliding frictional connection with the arm. So that the points at which the arm and the link are pivoted to the base and a connection point of the link and the arm form the apices of a triangle. The adjustable luminaire further comprises a torsion spring which is wound around the axis of a pin on which the link is pivoted to the base. When the arm is held upright, the link has a lost motion connection with the spring. When the link and the arm are swung to take up the lost motion connection, the spring is arranged to apply torque to the link to resist further movement of the link and the arm toward a more horizontal position, and to assist in returning link and arm from such a more horizontal position.
However, the link and the arm only pivotally move relative to the base due to the pin pivotally connecting the arm to the base and the torsion spring pivotally connecting the link to the base. As the lamp housing is moved downwardly or upwardly relative to the base, the illuminated area keeps the same. Therefore, when the lamp is close to the desk, the brightness is relatively high. When the lamp is far away from the desk, the brightness is relatively low. The inappropriate brightness causes a user uncomfortable.
The present invention has arisen to mitigate and/or obviate the disadvantages of the conventional adjustable luminaire.